Class REGULAR-EXPRESSION-TEMPLATE

Package:

COMMON-LISP.EXTENSIONS.DATA-AND-CONTROL-FLOW.UNIFICATION

Class Precedence List:

REGULAR-EXPRESSION-TEMPLATE, STRING-TEMPLATE, VECTOR-TEMPLATE, SEQUENCE-TEMPLATE, ARRAY-TEMPLATE, TYPE-TEMPLATE, TEMPLATE, STANDARD-OBJECT, T.

Known Subclasses:

None.

Slots:

None documented.

Description:

The REGULAR-EXPRESSION-TEMPLATE class denotes regular expressions (the CL-PPCRE regular expressions) that are used to unify against a STRING.

Template Syntax:

The spec syntax for a REGULAR-EXPRESSION-TEMPLATE is the following:

  #T(regular-expression REGEXP &optional unification-vars &rest keys)
  #T(regexp REGEXP &optional unification-vars &rest keys)
    

where

  REGEXP           ::= <a CL-PPCRE regexp string or tree>
  unification-vars ::= '(' variable* ')'
  keys             ::= <CL-PPCRE (constant) keys to be passed to CL-PPCRE:CREATE-SCANNER>
    

regular-expression and regexp are interchangeable. The unification-vars, if present, are unified (i.e., associated) with each group returned by the scanner created by CL-PPCRE:CREATE-SCANNER. The scanner is called by the appropriate UNIFY method.

Examples:

  cl-prompt> (unify "abcbca" #T(regexp "a(bc)*a"))
  #<ENVIRONMENT xxx>
  
  cl-prompt> (unify #T(regexp "a(cb)*a" (?foo)) "acbcba")
  #<ENVIRONMENT xyz>

  cl-prompt> (find-variable-value '?foo *)
  "cb"
  T
  

Affected By:

None.

Exceptional Situations:

Unifying an REGULAR-EXPRESSION-TEMPLATE against a non-STRING object results in an UNIFICATION-FAILURE error being signaled.

See Also:

UNIFY

Notes:

The underlying implementation uses CL-PPCRE. If CL-PPCRE is not available in the system, CL-UNIFICATION will not have REGULAR-EXPRESSION-TEMPLATE working.